Non-woven web

ABSTRACT

A non-woven web is disclosed.

FIELD OF THE INVENTION

This invention relates to a non-woven web.

BACKGROUND OF THE INVENTION

Meltblown fibers can be manufactured with very fine diameters, in therange of 1-10 microns, which is very advantageous in forming variouskinds of non-woven fabrics. However, meltblown fibers are relativelyweak in strength. To the contrary, spunbond fibers can be manufacturedto be very strong but have a much larger diameter, in the range of 15-50microns. Fabrics formed from spunbond are less opaque and tend toexhibit a rough surface since the fiber diameters are quite large. Inaddition, spinning of thermoplastic resins through a multi-rowspinnerette, according to the spinning technology taught in U.S. Pat.No. 5,476,616, is quite challenging because of the fast solidificationof the outer rows and/or columns of filaments. Due to this fastsolidification in the outer rows and/or columns, the filaments tend tobe larger and/or form rope defects with adjacent inner rows and/orcolumns of filaments.

The problem, up to now, is that no one has been able to find a way toextrude small fibers, having a diameter matching those of meltblownfibers, yet having the strength of spunbond fibers.

Now, a non-woven web has been invented which solves this problem.

SUMMARY OF THE INVENTION

Briefly, this invention relates to an apparatus and a process forforming a non-woven web, and the web itself. The apparatus for producinga non-woven web includes a die block having an inlet for receiving amolten material which communicates with a cavity. The die block also hasa gas passage through which pressurized gas can be introduced. The gaspassage has an inside diameter. An insert is positioned in the gaspassage and has an inside diameter and an outside diameter. A majorportion of the outside diameter is smaller than the inside diameter ofthe gas passage to form an air chamber therebetween. The apparatus alsoincludes a spinnerette secured to the die block which has a gas chamberisolated from the cavity. The spinnerette also has a gas passagewaywhich connects the gas chamber to the gas passage. A plurality ofnozzles and a plurality of stationary pins are secured to thespinnerette. The plurality of nozzles and the plurality of stationarypins are grouped into an array of a plurality of rows and a plurality ofcolumns, having a periphery. Each of the plurality of nozzles isconnected to the cavity. The apparatus further includes a gasdistribution plate secured to the spinnerette which has a plurality offirst, second and third openings formed therethrough. Each of the firstopenings surrounds one of the nozzles, each of the second openingssurrounds one of the stationary pins, and each of the third openings islocated adjacent to the first and second openings. The apparatus alsoincludes an exterior member secured to the gas distribution plate. Theexterior member has a plurality of first and second enlarged openingsformed therethrough. Each of the first enlarged openings surrounds oneof the nozzles and each of the second enlarged openings surrounds one ofthe stationary pins. The array of nozzles and stationary pins has atleast one row and at least one column, which are located adjacent to theperiphery, being made up of the second enlarged openings. Thepressurized gas exits through both the first and second enlargedopenings at a predetermined velocity. The molten material is extrudedinto filaments and each of the filaments is shrouded by the pressurizedgas to be solidified and attenuated into fibers. In addition, theperiphery around all of the extruded filaments/fibers is shrouded byanother pressurized gas curtain to isolate them from the surroundingambient air, essentially a dual shroud system. Lastly, the apparatusincludes a moving surface located downstream of the exterior member ontowhich the fibers are collected into a non-woven web.

The process for forming a non-woven web includes the steps of forming amolten polymer and directing the molten polymer through a die block. Thedie block has a cavity and an inlet connected to the cavity whichconveys a molten material therethrough. The die block also has a gaspassage formed therethrough for conveying pressurized gas. The gaspassage has an inside diameter. An insert is positioned in the gaspassage. The insert has an inside diameter and an outside diameter. Amajor portion of the outside diameter is smaller than the insidediameter of the gas passage to form an air chamber therebetween. Aspinnerette body is secured to the die block. The spinnerette body has agas chamber and a gas passageway connecting the gas chamber to the gaspassage. The spinnerette body has a plurality of nozzles and a pluralityof stationary pins secured thereto which are grouped into an array of aplurality of rows and a plurality of columns. The array has a periphery.A gas distribution plate is secured to the spinnerette body. The gasdistribution plate has a plurality of first, second and third openingsformed therethrough. Each of the first openings surrounds one of thenozzles, each of the second openings surrounds one of the stationarypins, and each of the third openings is located adjacent to the firstand second openings. An exterior member is secured to the gasdistribution plate. The exterior member has a plurality of first andsecond enlarged openings formed therethrough. Each of the first enlargedopenings surrounds one of the nozzles and each of the second enlargedopenings surrounds one of the stationary pins. The array of nozzles andstationary pins has at least one row and at least one column of thesecond enlarged openings which are located adjacent to the periphery.The extruded filament exiting each of the nozzles is shrouded by thepressurized gas to be solidified and attenuated into fibers. Inaddition, the periphery around all of the extruded filaments/fibers isshrouded by pressurized gas exiting each of said second enlargedopenings to isolate them from the surrounding ambient air, essentially adual shroud system. Lastly, the fibers are collected on a moving surfaceto form a non-woven web.

The nonwoven web of this invention has a plurality of fibers formed froma molten polymer with an average fiber diameter ranging from betweenabout 0.5 microns to about 50 microns, a basis weight of at least about0.5 grams per square meter (gsm), and a tensile strength, measured in amachine direction, which ranges from between about 10 gram force pergrams per square meter per centimeter width of the non-woven web(gf/gsm/cm) to about 50 gf/gsm/cm width of the non-woven web.

The general object of this invention is to provide an apparatus forforming a non-woven web. A more specific object of this invention is toprovide a process for forming a non-woven web and the web itself.

Another object of this invention is to provide a non-woven web which hasfine fibers, each having a diameter similar to the diameter of aconventional meltblown fiber, and having a comparable strength tospunbond fabrics.

A further object of this invention is to provide a non-woven web withfine fibers having a diameter ranging from between about 0.5 microns toabout 50 microns, a basis weight of at least about 0.5 gsm, and atensile strength of from between about 10 gf/gsm/cm width of thenon-woven web to about 50 gf/gsm/cm width of the non-woven web.

Still another object of this invention is to provide a die block wherethe incoming pressurized gas passages are thermally insulated from theremainder of the die block which allows for the use of gas having acolder temperature.

Still further, an object of this invention is to provide a processhaving a dual shroud system whereby each extruded filament is shroudedby pressurized gas as it is crystallized and attenuated into a fiber andall of the filaments/fibers are shrouded by pressurized gas to isolatethem from the surrounding ambient air.

Other objects and advantages of the present invention will become moreapparent to those skilled in the art in view of the followingdescription and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a process for forming a non-woven web.

FIG. 2 is a cross-sectional view of a die block, a spinnerette and anexterior plate secured together.

FIG. 3 is a vertical, cross-section of a perspective view of a die blockshowing a pair of gas passages.

FIG. 4 is an end view of a nozzle surrounded by an opening.

FIG. 5 is an end view of a stationary pin surrounded by an opening.

FIG. 6 is a partial exploded view of a portion of the spinnerette withinthe area labeled A in FIG. 2.

FIG. 7 is a perspective view of an array of nozzles arranged intoelongated rows aligned perpendicular to shorter length columns, with thetwo outside rows consisting of second openings, each of which houses astationary pin, and the three columns situated adjacent an end of thearray consisting of second openings, each of which houses a stationarypin.

FIG. 8 is a partial cross-sectional view of a portion of a spinnerettebody showing a plurality of nozzles flanked by two outside rows and anoutermost column containing second enlarged openings, each having astationary pin secured therein.

FIG. 9 is to front view of a gas distribution plate.

FIG. 10 is a front view of an exterior member.

FIG. 11 is a schematic of an alternative process for forming a non-wovenweb.

FIG. 12 is a pair of histograms comparing the difference in “FiberDiameter Distribution” for a non-woven web produced according to thisinvention and one produced using a conventional meltblown process.

FIG. 13 is a graph comparing machine direction (MD) tensile strength fora conventional meltblown web, a conventional spunbond web and anon-woven made according to this invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Non-woven is defined as a sheet, web or batt of natural and/or man-madefibers or filaments (excluding paper) that have not been converted intoyarns, and that are bonded to each other by mechanical,hydro-mechanical, thermal or chemical means.

Spunmelt is a process where fibers are spun from molten polymer througha plurality of nozzles in a die head connected to one or more extruders.The spunmelt process may include meltblowing, spunbonding and thepresent inventive process, which we call spunblowing.

Meltblown is a process for producing very fine fibers having a diameterof less than about 10 microns, where a plurality of molten polymerstreams are attenuated using a hot, high speed gas stream once thefilaments emerge from the nozzles. The attenuated fibers are thencollected on a flat belt or dual drum collector. A typical meltblowingdie has around 35 nozzles per inch and a single row of spinnerettes. Thetypical meltblowing die uses two inclined air jets for attenuating thefilaments.

Spunbond is a process for producing strong fibrous nonwoven websdirectly from thermoplastics polymers by attenuating the spun filamentsusing cold, high speed air while quenching the fibers near thespinnerette face. Individual fibers are then laid down randomly on acollection belt and conveyed to a bonder to give the web added strengthand integrity. Fiber size is usually below 250 μm and the average fibersize is in the range of from between about microns to about 50 microns.The fibers are very strong compared to meltblown fibers because of themolecular chain alignment that is achieved during the attenuation of thecrystallized (solidified) filaments. A typical spunbond die has multiplerows of polymer holes and the polymer melt flow rate is usually belowabout 500 grams/10 minutes.

The present invention is a hybrid process between a conventionalmeltblown process and a conventional spunbond process. The presentinvention bridges the gap between these two processes. The presentinvention uses a multi-row spinnerette similar to the spinnerette usedin spunbonding except the nozzles and stationary pins are arranged in aunique fashion to allow parallel gas jets surrounding the spun filamentsin order to attenuate and solidify them. In the present invention, eachof the extruded filaments is shrouded by pressurized gas and it'stemperature can be colder or hotter than the polymer melt. In addition,the periphery around all of the filaments is surrounded by a curtain ofpressurized gas, essentially a dual shroud system.

An alternative embodiment of the present invention uses an aspirator toattenuate the molten filaments into fibers. The aspirator uses highvelocity gas (air) that is directed essentially parallel to the flowdirection of the filaments, instead of being directed at a steep inclineangle thereto. The combination of these features produce fibers havingsmall or fine diameters, similar to conventional meltblown fibers, yetmuch stronger fibers, similar to conventional spunbond fibers. Theapparatus of the present invention is very flexible and versatile inthat it can accommodate both meltblown and spunbond polymer resins,which may have a melt flow rate of from between about 4 grams per 10minutes (g/10 min.) to about 6,000 g/10 min., according to the AmericanStandard Testing Method (ASTM) D 1238, at 210° C. and 2.16 kg.

Apparatus

Referring to FIG. 1, an apparatus 10 is shown for producing a non-wovenweb 12. The non-woven web 12 can have a high loft. A polymer resin 14,in the form of small solid pellets, is placed into a hopper 16 and isthen routed through a conduit 18 to an extruder 20. In the extruder 20,the polymer resin 14 is heated to an elevated temperature. Thetemperature will vary depending on the particular composition and melttemperature of a particular polymer. Usually, the polymer resin 14 isheated to a temperature at or above its melt temperature. The meltedpolymer resin 14 is transformed into a molten material (polymer) 22, seeFIG. 2, which is then routed through a conduit 24 to a die block 26having a spinnerette body 52 secured thereto.

The polymer resin 14 can vary in composition. The polymer resin can be athermoplastic. The polymer resin 14 can be selected from the groupconsisting of: polyolefins, polyesters, polyethylene terephthalates,polybutylene terephthalates, polycyclohexylene dimethyleneterephthalates, polytrimethylene terephthalates, polymethylmethacrylates, polyamides, nylons, polyacrylics, polystyrenes,polyvinyls, polytetrafluoroethylenes, ultrahigh molecular weightpolyethylenes, very high molecular weight polyethylenes, high molecularweight polyethylenes, polyether ether ketones, non-fibrous plasticizedcelluloses, polyethylenes, polypropylenes, polybutylenes,polymethylpentenes, low-density polyethylenes, linear low-densitypolyethylenes, high-density polyethylenes, polystyrenes,acrylonitrile-butadiene-styrenes, styrene-acrylonitriles, styrenetri-block and styrene tetra block copolymers, styrene-butadienes,styrene-maleic anhydrides, ethylene vinyl acetates, ethylene vinylalcohols, polyvinyl chlorides, cellulose acetates, cellulose acetatebutyrates, plasticized cellulosics, cellulose propionates, ethylcellulose, natural fibers, any derivative thereof, any polymer blendthereof, any copolymer thereof or any combination thereof. In addition,the polymer resin 14 can be selected from biodegradable thermoplasticsderived from natural resources, such as polylactic acid,poly-3-hydroxybutyrate, polyhydroxyalkanoates, or any blend, copolymer,polymer solutions or combination thereof. Those skilled in the chemicalarts may know of other polymers that can also be used to form thenon-woven web 12. It should be understood that the non-woven 12 of thisinvention is not limited to just those polymers identified above.

The non-woven web 12 can be formed from a homopolymer. The non-woven web12 can be formed from polypropylene. Alternatively, the non-woven web 12can be formed from two or more polymers. The non-woven web 12 cancontain bicomponent fibers wherein the fibers have a sheath-coreconfiguration with the core formed from one polymer and the surroundingsheath formed from a second polymer. Still another option is to producethe non-woven web 12 from bicomponent fibers where the fibers have aside-by-side configuration. Those skilled in the polymer arts will beaware of various fiber designs incorporating two or more polymers.

It should be understood that the non-woven web 12 can include anadditive which can be applied before or after the fibers are collected.Such additives can include, but are not limited to: a superabsorbent,absorbent particulates, polymers, nano-particles, abrasive particulates,active particles, active compounds, ion exchange resins, zeolites,softening agents, plasticizers, ceramic particle pigments, dyes,flavorants, aromas, controlled release vesicles, binders, adhesives,tackifiers, surface modification agents, lubricating agents,emulsifiers, vitamins, peroxides, antimicrobials, deodorizers, flameretardants, anti-foaming agents, anti-static agents, biocides,antifungals, degradation agents, stabilizing agents, conductivitymodifying agents, or any combination thereof.

Referring to FIG. 2, a cross-sectional view of a die block 26 andspinnerette body 52 is depicted. The molten material 22 enters the dieblock 26 through an inlet 28 which communicates with a cavity 30. Thecavity 30 can be an enlarged area where the molten material (polymer) isequalized. By “equalize” it is meant to make equal, uniform. Dependingupon the size of the die block 26, the cavity 30 can be several incheswide and up to several feet in length. The cavity 30 can contain polymerdistribution plates and filter screens (not shown).

Referring to FIGS. 2 and 3, the die block 26 has one or more gaspassages 32 formed therein. A pair of gas passages 32, 32 is shown inFIGS. 2 and 3. Each gas passage 32 has an inside diameter d. The insidediameter d can vary in dimension. The pressurized gas passing througheach of the gas passages 32, 32 is usually pressurized air.

It should be understood that in FIG. 3, the pair of gas passages 32, 32are offset from the inlet 28, and therefore the inlet 28 does not appearin FIG. 3.

Each of the pair of gas passages 32, 32 can vary in diameter, length andconfiguration. Each of the pair of gas passages 32, 32 can be linear,curved, angled, or have some other unique configuration. It has beenfound that by positioning a hollow insert 34 in each of the pair of gaspassages 32, 32, that one can better control the temperature of theincoming gas. By “gas” it is meant the state of matter distinguishedfrom the solid and liquid states by relatively low density and viscosityand the spontaneous tendency to become distributed uniformly throughoutany container; a substance in the gaseous state. In the apparatus 10, apressurized gas, most likely air, is introduced into the die block 26and spinnerette body 52. By “air” it is meant a colorless, odorless,gaseous mixture, mainly nitrogen (approximately 78%) and oxygen(approximately 21%) with lesser amounts of other gases.

The insert 34 can be a ceramic insert. By “ceramic” it is meant any ofvarious hard, brittle, heat and corrosion-resistant materials made byshaping and then firing a nonmetallic mineral, such as clay, at a hightemperature. Alternatively, the insert 34 can be constructed of variousother heat resistant materials. Still another option is to coat theinsert 34 with a heat resistant coating, such as a ceramic coating. Onecould also coat the insert 34 with some other material which has goodthermal insulation properties.

As best shown in FIG. 3, each of the inserts 34, 34 has an insidediameter d₁ and an outside diameter d₂. Desirably, the inside diameterd₁ is smooth. The inside diameter d₁ can vary depending upon the size ofthe die block 26. Typically, the inside diameter d₁ ranges from betweenabout 0.1 inches to about 1 inch. Desirably, the inside diameter d₁ isat least 0.25 inches in diameter. More desirably, the inside diameter d₁is at least 0.3 inches in diameter. Even more desirably, the insidediameter d₁ is at least 0.4 inches in diameter. Most desirably, theinside diameter d₁ is around 0.5 inches.

Each insert 34 has a first end 36 and a second end 38. The first end 36is spaced apart from the second end 38. The first end 36 is aligned withan exterior surface 42 of the die block 26 and the second end 38 isaligned with an inner surface 40 of the die block 26. The first end 36contains an outwardly protruding flange 44 and the second end 38 alsocontains an outwardly protruding flange 46. By “flange” it is meant aprotruding rim, edge, rib or collar, as on a pipe shaft, used tostrengthen an object, hold it in place or attach it to another object.The structural shape of the flanges, 44 and 46, create a physicalchamber 48 in a bore hole 50, which is machined into the die block 26,and in which each insert 34 is fitted. Each of the pair of inserts 34,34 is fitted into one of the pair of bore holes, 50, 50. The chambers48, 48 are located between the inside diameter d of each bore hole 50and the outside diameter d₂ of each of the pair of inserts 34, 34. Eachchamber 48 extends longitudinally along a portion of the insert 34between the two flanges, 44 and 46. Desirably, each chamber 48 willextend along a major portion of the outside diameter d₂ of each of thepair of inserts 34, 34. Each chamber 48 can be filled with a gas, suchas air. Each chamber 48 functions as a thermal insulator that limitsheat transfer from the hot, die block 26 to the pressurized gas passingthrough the inside diameter d₁ of each of the pair of inserts 34, 34.Because of this, no cold spots will develop in the die block 26. Inaddition, the hot die block 26 will not heat up the incoming pressurizedgas that is being routed to the spinnerette body 52. The combination ofthe pair of inserts 34, 34 and the adjacent chambers 48, 48, enable theoperator to direct the pressurized gas (air) through the die block 26without affecting the temperature of either the die block 26 or theincoming pressurized gas (air) significantly. Because of this, muchcolder pressurized gas (air) can be utilized in this inventive process.This colder pressurized gas (air) can enhance fiber crystallization(solidification of the extruded filaments into fibers) and increase thefiber tensile properties.

Still referring to FIG. 3, the size, shape and configuration of thechambers 48, 48 can vary. Desirably, each of the chambers 48, 48 has aheight h ranging from between about 0.01 inches to about 0.3 inches.More desirably, the height h of each chamber 48, 48 can range frombetween about 0.05 inches to about 0.25 inches. Even more desirably, theheight h of each chamber 48, 48 can range from between about 0.1 inchesto about 0.2 inches. Most desirably, the height h of each chamber 48, 48is greater than about 0.12 inches.

The presence of the chambers 48, 48, in combination with the materialfrom which the inserts 34,34 are made of, or coated with, will assureone that the pressurized gas (air) that is routed through the inserts34, 34 will not be heated a substantial amount due to the temperature ofthe die block 26. In other words, the inserts 34, 34, in combinationwith the chambers 48, 48 function to provide thermal insulation andlimit heat transfer.

It should be understood that the inside diameter d of each of the boreholes 50, 50 can also be coated with a ceramic coating to provideanother layer of heat insulation, if desired.

A die block 26 is constructed out of a mass of metal or steel which is agood conductor of heat. The heavy mass of the die block 26 also causesit to retain any heat that is conveyed to it. The temperature of the dieblock 26 is elevated above ambient temperature due to the moltenmaterial 22 (polymer) flowing through the die block 26 and due toheating cartages (not shown) that prevent the polymer melt from beingsolidified by the cold ambient air or the process air. By “ambienttemperature” it is meant the surrounding temperature, such as roomtemperature. The melt temperature of the various molten material 22(polymer) does vary but usually exceeds 100° C. For many polymers, themelt temperature can be as high as 200° C., 250° C., 300° C., 350° C.,400° C., or even higher. By thermally insulating the incomingpressurized gas (air) from the elevated temperature in the die block 26,one can better control the entire process and produce extruded filamentsand fibers that are very precise in composition, diameter and strength.

Referring again to FIG. 2, the apparatus 10 also includes a spinnerettebody 52. By “spinnerette” it is meant a device for making syntheticfibers, consisting of a plate pierced with holes through which plasticmaterial (polymer) is extruded in filaments. The spinnerette body 52 issecured to the die block 26. The die block 26 and the spinnerette body52 have essentially the same length and width. Usually the perimeters ofeach are coterminous. The die block 26 and the spinnerette body 52 eachhave a generally rectangular configuration. The spinnerette body 52 hasa length l, see FIG. 1 and a width w, see FIG. 2. The length l is longerthan the width w. The spinnerette body 52 has a gas chamber 54. One ormore gas passageways 56, 56 are formed in the spinnerette body 52. Apair of gas passageways 56, 56 is depicted in FIG. 2, with each beingconnected to one of the pair of gas passages 32, 32. The pair of gaspassageways 56, 56 connect the gas chamber 54 to the pair of gaspassages 32, 32 so that pressurized gas (air) can be introduced into thegas chamber 54. The source of the pressurized gas (air) is not shown inthe drawings but equipment to produce the pressurized gas (air) is wellknown to those skilled in the arts.

It should be understood that the gas chamber 54 is separate and distinctfrom the cavity 30 formed in the die block 26. In other words, the gaschamber 54 is isolated from the cavity 30. By “isolate” it is meant toset apart or cut off from others, to render free of external influences;insulate. This means that the molten material 22 is not in contact withthe pressurized gas (air) while it is in the cavity 30.

It should be understood that the spinnerette body 52 could be coatedwith a ceramic coating, if desired.

The apparatus 10 further includes a plurality of nozzles 58. By “nozzle”it is meant a projecting part with an opening, as at the end of a hose,for regulating and directing the flow of a fluid or molten material.Each of the nozzles 58 is secured to the spinnerette body 52. Each ofthe nozzles 58 is spaced apart from an adjacent nozzle 58. In thespinnerette body 52, the number of nozzles 58 can vary. A spinnerettebody 52 can contain from as few as ten nozzles 58 to several thousandnozzles 58. For a commercial size line, the number of nozzles 58 in thespinnerette body 52 can range from between about 1,000 to about 10,000.Desirably, the spinnerette body 52 will have at least about 1,500nozzles. More desirably, the spinnerette body 52 will have at leastabout 2,000 nozzles. Even more desirably, the spinnerette body 52 willhave at least about 2,500 nozzles. Most desirably, the spinnerette body52 will have 3,000 or more nozzles.

The size of the nozzles 58 can vary. The size of the nozzles 58 canrange from between about 50 microns to about 1,000 microns. Moredesirably, the size of the nozzles 58 can range from between about 150microns to about 700 microns. More desirably, the size of the nozzles 58can range from between about 20 microns to about 600 microns. Nozzles ofvarious size can be used but generally all of the nozzles have the samesize.

Referring to FIGS. 2, 4 and 6, each of the nozzles 58 can be formed froma metal, such as steel, stainless, a metal alloy, a ferrous metal, etc.Desirably, each of the nozzles 58 is formed from stainless steel. Eachof the nozzles 58 is depicted as an elongated, hollow tube 60, see FIGS.2 and 6. By “tube” it is meant a hollow cylinder, especially one thatconveys fluid or functions as a passage. Each of the hollow, cylindricaltubes 60 is open at each end and has a longitudinal central axis and auniquely shaped inside cross-section. Desirably, the insidecross-section of each tube 60 is circular in shape and constantthroughout its length. The length of each of the nozzles 58 can vary.Typically, the length of a nozzle 58 ranges from between about 0.5 toabout 6 inches.

It should be understood that the nozzles 58 can be of any geometricalshape, although a circular shape is favored.

Each of the nozzles 58, in the form of a hollow, cylindrical tube 60,has an inside diameter d₃ and an outside diameter d₄. The insidediameter d₃ can range from between about 0.125 millimeters (mm) to about1.25 mm. The outside diameter d₄ of each nozzle 58 should be at leastabout 0.5 mm. Desirably, the outside diameter d₄ of each nozzle 58 canrange from between about 0.5 mm to about 2.5 mm.

The molten material 22 (polymer) is extruded through the inside diameterd₃ of each nozzle 58. The back pressure on the molten material 22(polymer), present in each of the hollow, cylindrical tubes 60, shouldbe equal to or exceed about 5 bar. By “bar” it is meant a unit ofpressure equal to one million (10⁶) dynes per square centimeter.Desirably, the back pressure on the molten material 22 (polymer),present in each of the hollow, cylindrical tubes 60, can range frombetween about 20 bar to about 200 bar depending on the polymerproperties and the operating conditions. More desirably, the backpressure on the molten material 22 (polymer), present in each of thehollow, cylindrical tubes 60, can range from between about 25 bar toabout 150 bar. Even more desirably, the back pressure on the moltenmaterial 22 (polymer), present in each of the hollow, cylindrical tubes60, can range from between about 30 bar to about 100 bar.

Referring again to FIG. 2, the apparatus 10 also includes a plurality ofstationary pins 62. Each of the stationary pins 62 is an elongated,solid member having a longitudinal central axis and an outside diameterd₅. Each of the stationary pins 62 is secured to the spinnerette body 52and usually they have a similar outside diameter to the polymer nozzles58. The outside diameter d₅ of each of the stationary pins 62 shouldremain constant throughout its length. The dimension of the outsidediameter d₅ can vary. Desirably, the outside diameter d₅ of each of thestationary pins 62 is at least about 0.25 mm. More desirably, theoutside diameter d₅ of each of the stationary pins 62 is at least about0.5 mm. Even more desirably, the outside diameter d₅ of each of thestationary pins 62 is at least about 0.6 mm. Most desirably, the outsidediameter d₅ of each of the stationary pins 62 is at least about 0.75 mm.

Referring now to FIGS. 7 and 8, the plurality of nozzles 58 and theplurality of stationary pins 62 are grouped into an array of a pluralityof rows 64 and a plurality of columns 66, having a periphery 68. By“array” it is meant an orderly arrangement. The number of rows 64 canvary as well as the number of columns 66. Typically, the number of rows64 will range from between about 2 to about 50. Desirably, the number ofrows 64 will range from between about 3 to about 30. More desirably, thenumber of rows 64 will range from between about 4 to about 25. Even moredesirably, the number of rows 64 will range from between about 4 toabout 20. Most desirably, the number of rows 64 will range from betweenabout 5 to about 15.

Typically, the number of columns 66 will range from about 50 to about500. Desirably, the number of columns 66 will range from about 60 toabout 450. More desirably, the number of columns 66 will range fromabout 100 to about 300. Even more desirably, the number of columns 66will range from about 150 to about 250. Most desirably, the number ofcolumns 66 will be greater than 200.

The spinnerette body 52 will have a nozzle density ranging from betweenabout 30 nozzles per centimeter to about 200 nozzles per centimeter.Desirably, the nozzle density will be over 50 nozzles per centimeter.More desirably, the nozzle density will be over 75 nozzles percentimeter. Even more desirably, the nozzle density will be over 100nozzles per centimeter. Most desirably, the nozzle density will be over150 nozzles per centimeter.

The polymer throughput through each nozzle 58 is stated in “gram perhole per minute” (ghm). The polymer throughput through each nozzle 58can range from between about 0.01 ghm to about 4 ghm.

The finished diameter of each of the extruded and attenuated fibers isbelow about 50 microns. The average fiber diameter is from between about0.5 microns to about 50 microns, with a standard deviation above 0.5microns. Desirably, the average fiber diameter is from between about 1micron to about 50 microns, with a standard deviation above 0.5 microns.More desirably, the average fiber diameter is from between about 1micron to about 30 microns, with a standard deviation above 0.5 microns.Even more desirably, the average fiber size is from between about 1micron to about 20 microns, with a standard deviation above 0.5 microns.Most desirably, the average fiber size is from between about 1 micron toabout 10 microns, with a standard deviation above 0.5 microns.

The periphery 68 is indicated by a line extending around the outside ofthe plurality of nozzles 58 and the plurality of stationary pins 62. Therows 64 are shown as being long lines extending horizontally in theapparatus 10 while the columns 66 are shorter in length and are alignedperpendicular to the rows 64. By “perpendicular” it is meantintersecting at or forming a right angle (90 degrees). Although the rows64 and the columns 66 are shown as being aligned perpendicular to eachother, one can certainly use different angular alignments, if desired.The rows 64 and the columns 66 are also depicted as being arranged inparallel rows 64 and parallel columns 66. By “parallel” it is meantbeing an equal distance apart everywhere. However, one could stagger therows 64 and/or the columns 66, if desired. The number of rows 64 canvary as can the number of columns 66.

In FIG. 7, one will notice that the two outside rows 64, 64 locatedadjacent to the two longitudinal sides of the periphery 68 of the arrayof rows 64 and columns 66, does not contain nozzles 58. In addition, thethree columns 66 at the end of the array also do not contain any nozzles58. One can utilize the stationary pins 62 in as many rows 64 andcolumns 66, located adjacent to the periphery 68, as desired. Typically,only 1 or 2 rows adjacent to the outer periphery 68 of the array arevoid of nozzles 58, while from between about 1 to about 50 of thecolumns 66 can be void of a nozzle 58. The exact number of columns 66which do not contain the nozzles 58 will depend partly on the overallsize of the spinnerette body 52. The reason for not positioning nozzles58 in such rows 64 and columns 66 is that in a rectangular exteriormember 78, see FIG. 2, having about twelve rows 64 and having more thanabout 150 columns 66, there are simply more columns 66 present.Therefore, one could eliminate more nozzles 58 from the columns 66 thanfrom the rows 64. In addition, by narrowing the array of nozzles 58 in aspinnerette body 52, one can better maintain constant temperature valuesbetween the plurality of nozzles 58 being utilized.

As mentioned above, the total number of nozzles 58 and stationary pins62 that can be secured to the spinnerette body 52 can vary. The largerthe size of the spinnerette body 52, the more nozzles 58 and stationarypins 62 that it can support. For a typical commercial spinnerette body52, it will have several rows 64 and many more columns 66. The number ofrows 64 can vary but generally will range from about 4 to about 20. Thenumber of columns 66 can also vary but generally will range from about50 to about 500. Desirably, a commercial size spinnerette body 52 willhave about 8 to about 16 rows and from between about 100 to about 300columns. For example, a spinnerette body 52 containing a total of 2,496combined nozzles 58 and stationary pins 62 could have twelve rows 64 andtwo hundred and eight columns 66.

Referring now to FIGS. 2 and 9, the apparatus 10 further includes a gasdistribution plate 70 secured to the spinnerette body 52. The gasdistribution plate 70 functions to distribute the pressurized gas (air)equally around each of the nozzles 58 to ensure proper filamentattenuation. The gas distribution plate 70 can vary in thickness,configuration and material from which it is formed. Desirably, the gasdistribution plate 70 is constructed out of metal or steel. Moredesirably, the gas distribution plate 70 is constructed out of stainlesssteel. The gas distribution plate 70 has multiple openings formedtherethrough. The multiple openings include a plurality of firstopenings 72 through which the plurality of nozzles 58 can pass, aplurality of second openings 74 through which the plurality ofstationary pins 62 can pass, and a plurality of third openings 76through which pressurized gas (air) can pass. The exact number of first,second and third openings 72, 74 and 76 can vary depending upon the sizeof the spinnerette body 52 and the total number nozzles 58 andstationary pins 62 being utilized. The first and second openings, 72 and74 respectively, must align with the array of nozzles 58 and stationarypins 62 secured to the spinnerette body 52. No extra or unused first andsecond openings, 72 and 74 respectively, should be formed through thegas distribution plate 70.

The plurality of first, second and third openings, 72, 74 and 76respectively, are all shown as being circular openings having apredetermined diameter. This assumes that each of the plurality ofnozzles 58 and each of the plurality of stationary pins 62 have acircular outside diameter. The geometrical shape of the third openings76 do not have to be circular, if desired. However, it is much more costeffective to form a circular hole than some other shape and therefore,from a practical point of view, the third openings 76 will also mostlikely have a circular outside diameter.

Each of the plurality of first openings 72 are sized and configured tomatch or be slightly larger than the outside diameter d₄ of theplurality of nozzles 58. A tight, snug or press fit can be utilized toretain the plurality of nozzles 58 in a set arrangement. Each of theplurality of second openings 74 are sized and configured to match or beslightly larger than the outside diameter d₅ of the plurality ofstationary pins 62. Again, a tight, snug or press fit can be utilized toretain the plurality of stationary pins 62 in a set arrangement. Each ofthe plurality of third openings 76 are sized and configured to allow anappropriate amount of pressurized gas (air) to pass through them. Theamount of pressurized gas (air) that is needed can be calculated basedupon a number of factors, such as the composition of the molten material22 (polymer) that is being extruded, the number of nozzles 58 andstationary pins 62 that are present, the inside diameter d₃ of each ofthe nozzles 58, the flow rate of the molten material 22 (polymer)passing through each of the nozzles 58, the velocity of the pressurizedgas (air) passing through the gas distribution plate 70, etc. By“velocity” it is meant the rapidity or speed of motion, swiftness. Thoseskilled in the art can easily calculate the amount of pressurized gas(air) that is needed, its velocity and a temperature which isadvantageous to running the apparatus 10 at a maximum speed.

Still referring to FIG. 9, one can clearly see that each of the firstand second openings, 72 and 74 respectively, can be of the samediameter. Alternatively, the diameter of the first openings 72 can besized to be smaller or larger than the diameter of the second openings74. When the outside diameter d₄ of each of the plurality of nozzles 58is the same as the outside diameter d₅ of each of the plurality ofstationary pins 62, then the diameter of each of the first openings 72will be equal to the diameter of each of the second openings 74.

One will also notice that in FIG. 9, that the second openings 74 are alllocated around the outer periphery 68 of the plurality of the firstopenings 72. By “periphery” it is meant a line that forms the boundaryof an area; a perimeter. The reason for this arrangement is that asecond shroud or curtain of pressurized gas (air) is obtained whichshelters the extruded filaments from the surrounding ambient air. Thisis a unique feature of the present invention.

Likewise, one can clearly see that each of the third openings 76 issmaller than the outside diameters of either the first openings 72 orthe second openings 74. However, if one wished to size the outsidediameter of each of the third openings 76 to be larger than or match theoutside diameter d₄ and d₅ of each of the first and second openings, 72and 74 respectively, this could easily be accomplished, especially ifsmall polymer nozzles 58 are being used. One drawback with making thethird openings 76 larger is that the rows 64 and columns 66 would thenhave to be spaced farther apart. This would limit the total number ofnozzles 58 and stationary pins 62 that could be secured to thespinnerette body 52.

Still referring to FIG. 9, one can clearly see that four of the thirdopenings 76 are positioned adjacent to each of the first and secondopenings, 72 and 74 respectively. The exact number of third openings 76associated with each of the first and second openings, 72 and 74 canvary. Likewise, the arrangement and angular spacing of the thirdopenings 76 relative to each of the first and second openings, 72 and 74respectively, can also vary. Furthermore, the distance that each of thethird openings 76 is spaced apart from the first and second openings, 72and 74 respectively, can also vary.

It should be understood that the gas distribution plate 70 could becoated with a ceramic coating, if desired.

Referring now to FIGS. 2 and 10, the apparatus 10 further includes anexterior member 78. The exterior member 78 is secured to the gasdistribution plate 70 so that it is spaced apart from the spinnerettebody 52. The exterior member 78 functions to form annular pressurizedgas (air) channels around each of the nozzles 58. The exterior plate 78can vary in thickness, configuration and material from which it isformed. Desirably, the exterior plate 78 is constructed out of metal orsteel. More desirably, the exterior plate 78 is constructed out ofstainless steel. The exterior plate 78 has multiple openings formedtherethrough, some are first enlarged openings 80, through which one ofthe nozzles 58 passes, and the remainder are second enlarged openings82, in which one of the stationary pins 62 is present. Each of the firstenlarged openings 80 accommodates a nozzle 58 and each of the secondenlarged openings 82 accommodates a stationary pin 62.

It should be understood that the exterior member 78 could be coated witha ceramic coating, if desired.

Referring to FIG. 10, one can clearly see that the second enlargedopenings 82 are all located around the outer periphery 84 of theplurality of the first enlarged openings 80. The reason for thisarrangement is that it provides a shroud around the periphery 84 of theplurality of nozzles 58 and prevents the surrounding ambient air fromcontacting the extruded filaments, such that the filaments do not cooltoo quickly.

Referring back to FIGS. 4 and 5, one will also notice that each of thefirst enlarged openings 80 has an inside diameter d₆ and each of thesecond enlarged openings 82 has an inside diameter d₇. The diameter d₆of the first enlarged opening 80 can be equal to the diameter d₇ of thesecond enlarged opening 82. Alternatively, the diameter d₆ of the firstenlarged opening 80 can be smaller or larger than the diameter d₇ of thesecond enlarged opening 82.

Referring to FIG. 10, the diameter d₆ of each of the first enlargedopenings 80 is identical to the diameter d₇ of each of the secondenlarged openings 82. Furthermore, when one compares the first andsecond openings, 72 and 74 respectively, shown in FIG. 9, to the firstand second enlarged openings, 80 and 82 respectively, shown in FIG. 10,one can see that the first and second enlarged openings, 80 and 82respectively, are much larger. The reason for this is that thepressurized gas (air) will exit through each of the first and secondenlarged openings, 80 and 82 respectively, and form a shroud around eachof the nozzles 58 and around each of the stationary pins 62. By “shroud”it is meant something that conceals, protects or screens. When the firstand second enlarged openings, 80 and 82 respectively, are circles, theshroud of pressurized gas (air) can completely encircle (360°) each ofthe nozzles 58 and each of the stationary pins 62.

Referring again to FIG. 7, one can see that each of the plurality ofnozzles 58 is centrally aligned in each of the first enlarged openings80. Likewise, each of the plurality of stationary pins 62 is centrallyaligned in each of the second enlarged openings 82. The reason for thisis that the shroud of pressurized gas (air) will then be evenlydistributed around the outer periphery of each of the nozzles 58 andaround the outer periphery of each of the stationary pins 62. Thepressurized gas (air) shrouds each of the nozzles 58 and assists incausing the extruded molten material 22 (polymer) to solidify andattenuate. In addition, one can see that in the array of nozzles 58 andstationary pins 62, at least one row 64 and at least one column 66 arearranged such that the second enlarged openings 82 are located adjacentto the periphery 84 of the first enlarged openings 80. This means thatat least the outside row 64 and at least the outermost column 66,located adjacent to the four sides of the exterior plate 78, willcontain only second enlarged openings 82. The reason for thisconfiguration is that it provides a shroud or curtain of pressurized gas(air) around all of the plurality of nozzles 58. This second shroud ofpressurized gas (air) will limit or prevent the quick solidification ofthe filaments which is caused when they are contacted by the surroundingambient air in the facility where the extruder 20 is housed.

Referring again to FIG. 2, as the pressurized gas exits from each of thefirst enlarged openings 80, adjacent to the plurality of nozzles 58 at apredetermined velocity, the molten material 22 (polymer) is extrudedinto filaments 86. Each of the filaments 86 is shrouded by thesurrounding pressurized gas from an adjacent filament 86 to preventroping. By “filament” it is meant a fine or thinly spun material stillin a semi-soften state. By this arrangement, contact between adjacentfilaments 86, 86 is prevented. In addition, the pressurized gas (air)exiting from each of the plurality of second enlarged openings 82 formsa shroud around all of the extruded filaments 86. This second shroudshelters the semi-molten filaments 86, 86 from the surrounding ambientair and slows down the cooling of the filaments 86, 86. By increasingthe time it takes each of the filaments 86 to cool, one can obtain finerdiameter fibers 98 and more accurately control the characteristics ofeach fiber 98. This feature of using a double shroud plus a second stageof fiber attenuation using an aspirator, which will be explained below,is very unique.

Still referring to FIGS. 2 and 7, the apparatus 10 further includes apair of cover strips 88, 88 secured to the exterior member 78. Each ofthe pair of cover strips 88, 88 consists of a separate and distinctmember that is spaced apart from the other member. Alternatively, thepair of cover strips 88, 88 could be manufactured as a single member.Each of the pair of cover strips 88, 88 is shown as having an exteriorsurface 90, 90. Each of the pair of cover strips 88, 88 extend along thelength l of the spinnerette body 52. As shown, each of the pair of coverstrips 88, 88 is aligned parallel to one another. Each of the externalsurfaces 90, 90 can have a beveled portion 92. The beveled portion 92extends downward and inward from the exterior surface 90. By “beveled”it is meant the angle or inclination of a line or surface that meetsanother at any angle but 90°. The beveled surfaces 92, 92 extendlongitudinally along the length l of the spinnerette body 52. The angleα of each of the beveled surfaces 92, 92 can vary. Desirably, the eachbeveled surface 92, 92 is formed at an angle α (see FIG. 2) which canrange from between about 15° to about 75°.

Still referring to FIG. 2, the pair of cover strips 88, 88 can be formedfrom a metal, such as steel, stainless, a metal alloy, a ferrous metal,etc. Desirably, the pair of cover strips 88, 88 is formed from stainlesssteel. The pair of cover strips 88, 88 facilitates the flow of ambientair around the pressurized gas exiting at least some of the secondenlarged openings 82. The pair of cover strips 88, 88 will direct theflow of ambient air around the lower portion of the exterior member 78such that this air will move according to the directions indicated bythe arrows 94, 94. The ambient air will follow the directions of thebeveled surfaces 92, 92 and then be turned downward away from theplurality of nozzles 58 by the exiting pressurized gas (air) forcefullyexiting the second enlarged openings 82. The exiting pressurized gas(air) is coming from the gas chamber 54 via the third openings 76 formedin the gas distribution plate 70 and via the second enlarged openings 82formed in the exterior member 78.

The pair of cover strips 88, 88 also functions to redistribute theclamping force exerted on the exterior member 78 and the gasdistribution plate 70 to secure them to the spinnerette body 52. Thepair of cover strips 88, 88 also function to protect the nozzles 58 fromthe entrained air in the room that may be drawn in from the sides andwhich could have a cooling effect on the outer rows.

Referring now to FIGS. 2 and 6, the molten material 22 (polymer) presentin the cavity 30 of the die block 26 is forced downward through theplurality of nozzles 58 and flows through the hollow cylindrical tubes60. Each nozzle 58 has a terminal end 96 which is located below theplane of the exterior member 78. Desirably, each terminal end 96 islocated below the plane of the exterior surface 90 of the pair of coverstrips 88, 88. Each nozzle 58 extends downward beyond the first enlargedopening 80 by a vertical distance d₈, see FIG. 6. The distance d₈ canvary. Desirably, the distance d₈ should be at least about 1 mm. Moredesirably, the distance d₈ is at least about 2 mm. Even more desirably,the distance d₈ is at least about 3 mm. Most desirably, the distance d₈is at least about 5 mm.

Referring to FIG. 2, the molten material 22 (polymer) exits each of theplurality of nozzles 58 as filaments 86. Each of the filaments 86 isisolated by the pressurized gas (air) exiting from the first enlargedopenings 80. This pressurized gas (air) provides a shroud or veil whichlimits a filament 86 from contacting, touching and/or bonding to anadjacent filament 86 and forming ropes and/or bundles. By “veil” it ismeant something that conceals, separates or screens like a curtain. Thevelocity and pressure at which the filaments 86 exit the plurality ofnozzles 58 can be varied to suit one's equipment and to form fibers 98,see FIG. 1, which meet certain fiber criteria, such as a particulardiameter, composition, strength, etc.

The temperature of the pressurized gas (air) used in shrouding andattenuating the filaments 86 at or near the nozzles 58 can be at a lowertemperature, the same temperature, or at a higher temperature, than themelt temperature of the passing filaments 86. Desirably, the temperatureof the pressurized gas (air) used in shrouding and attenuating thefilaments 86 at or near the nozzles 58 is at a temperature ranging frombetween about 0° C. to about 250° C. colder or hotter than the melttemperature of the filaments 86. More desirably, the temperature of thepressurized gas (air) used in shrouding and attenuating the filaments 86at or near the nozzles 58 is at a temperature ranging from between about0° C. to about 200° C. colder or hotter than the melt temperature of thefilaments 86. Even more desirably, the temperature of the pressurizedgas (air) used in shrouding and attenuating the filaments 86 at or nearthe nozzles 58 is at a temperature ranging from between about 0° C. toabout 150° C. colder or hotter than the melt temperature of thefilaments 86. Most desirably, the temperature of the pressurized gas(air) used in shrouding and attenuating the filaments 86 at or near thenozzles 58 is at a temperature ranging from between about 0° C. to about100° C. colder or hotter than the melt temperature of the filaments 86.

The pressurized gas (air) emitted through the multiple second openings82 will form pressurized gas (air) streams which will limit or preventthe plurality of filaments 86 from being contacted by the surroundingambient air. Desirably, this pressurized gas (air) can form an envelope,shroud or curtain around the entire circumference or periphery 84 of thetotal number of filaments 86. The velocity and pressure at which thefilaments 86 exit the plurality of nozzles 58 can be varied to suitone's equipment and to form fibers 98, see FIG. 1, which meet certainfiber criteria, such as a particular diameter, composition, strength,etc.

Referring now to FIG. 11, an alternative apparatus 10′ is shown whichincludes an aspirator 100. The aspirator 100 is located downstream ofthe terminal end 96 of each of the nozzles 58. By “aspirator” it ismeant a device for producing high speed gas (air) jets to drag andattenuate the filaments 86. The aspirator 100 is vertically aligneddownstream of the plurality of filaments 86 such that the plurality offilaments 86 can easily pass therethrough. Pressurized gas (air) isintroduced into the aspirator 100 via one or more conduits 102. A pairof conduits 102, 102 is depicted in FIG. 11. The number of conduits 102can vary from 1 to several. The incoming pressurized gas (air) enteringthe aspirator 100 is aligned parallel to the flow direction of thefilaments 86. This parallel gas (air) flow feature is important asparallel gas (air) jets will exert drag force on the filaments 86causing them to be under tension which will result in drawing thefilaments 86 into fibers 98. The incoming pressurized air to theaspirator 100 can be chilled, be at room temperature, or be heated.Typically, the incoming air is at room temperature or slightly higher.As the filaments 86 pass through the aspirator 100, they are attenuatedinto fibers 98 by the pressurized gas (air) travelling through theaspirator 100 at a velocity that is at least twice as great as thevelocity of the pressurized gas (air) exiting the plurality of first andsecond enlarged openings, 80 and 82 respectively. By “attenuate” it ismeant to make slender, fine or small. Desirably, the pressurized gas(air) used to attenuate the filaments 86 into fibers 98 is moving at avelocity that is at least 2.5 times greater than the velocity of thepressurized gas (air) exiting the plurality of first and second enlargedopenings, 80 and 82 respectively. More desirably, the pressurized gas(air) used to attenuate the filaments 86 into fibers 98 is moving at avelocity that is at least 5 times greater than the velocity of thepressurized gas (air) exiting the plurality of first and second enlargedopenings, 80 and 82 respectively. Even more desirably, the pressurizedgas (air) used to attenuate the filaments 86 into fibers 98 is moving ata velocity that is at least 10 times greater than the velocity of thepressurized gas (air) exiting the plurality of first and second enlargedopenings, 80 and 82 respectively. Most desirably, the pressurized gas(air) used to attenuate the filaments 86 into fibers 98 is moving at avelocity that is more than 10 times as great as the velocity of thepressurized gas (air) exiting the plurality of first and second enlargedopenings, 80 and 82 respectively. For example, the pressurized air usedto attenuate the filaments 86 into fibers 98 can have a velocity of atleast about 50 meters per second (m/s), about 100 m/s, 200 m/s, about250 m/s, about 300 m/s, about 400 m/s or greater.

The aspirator 100 functions as a second stage to attenuate the filaments86 so that they acquire similar strength properties to fibers formedusing conventional spunbond technology.

Referring back to FIG. 1, it should be noted that when an aspirator 100is not present, slightly heated gas (air) is used to achieve high fiberattenuation at or near the terminal end 96 of each of the nozzles 58.The produced fibers 98 tend to be weaker than conventional spunbondfibers but are still much stronger than conventional meltblown fibers.This is especially true when the temperature of the pressurized gas(air) is around 50° C. to about 100° C. lower than the polymer melttemperature. The inventive apparatus and process taught herein is veryversatile and is easily adjusted to fabricate spunmelt fibers 98 havinga wide range of properties. Such properties span the distance betweenconventional meltblown fibers to conventional spunbond fibers.

Referring again to FIG. 11, the number of fibers 98 exiting theaspirator 100 will be equal to the number of filaments 86 which enterthe aspirator 100. However, the fibers 98 will have a smaller diameterthan the diameter of each filament 86. In addition, the fibers 98 willgenerally be stronger than the filaments 86. The diameter of each fiber98 will be partially dictated by the amount that each filament 86 isattenuated in the aspirator 100. As the fibers 98 exit the aspirator100, they are directed downward and collected on a moving surface 104.

Referring to FIGS. 1 and 11, the moving surface 104 can vary in designand construction. For example, the moving surface 104 can be a movable,closed loop forming wire 106 mounted and supported by two or morerollers 108. One of the rollers 108 can be a drive roller. Four rollers108 are shown in FIGS. 1 and 11. The moving surface 104 can rotateclockwise or counter clockwise. Alternatively, the moving surface 104could be a conveyor belt, a rotatable drum, a forming drum, a dual drumcollector, or any other mechanism known to those skilled in the art.

The moving surface 104 can be operated at room temperature, especiallywhen the forming wire 106 or conveyor belt is constructed frompolyethylene terephthalate (PET) material. However, when the movingsurface 104 is constructed from metal or steel wire, or is covered withmetal belts, it can be heated slightly to impose specific textures orpatterns that may enhance the characteristics of the non-woven web 12.

The moving surface 104 can move at varying speeds that can influence thecomposition, density, integrity, etc. of the finished non-woven web 12.For example, as the speed of the moving surface 104 is increased, theloft or thickness of the non-woven web 12 will decrease.

Still referring to FIGS. 1 and 11, the apparatus 10 or 10′ furtherincludes a vacuum chamber 110 positioned adjacent to the moving surface104. As depicted, the vacuum chamber 110 is positioned below the formingwire 106. The vacuum chamber 110 applies a vacuum or suction to theplurality of randomly collected fibers 98 that form the non-woven web12. This vacuum will pull the process gas (air) and the ambient air awayfrom the non-woven web 12 and will also limit or prevent the fibers 98from flying around and thereby enhances uniformity of the non-woven web12. Various kinds of vacuum chambers 110 can be used. The amount ofvacuum applied can be varied to suit one's particular needs. Thoseskilled in the art are well aware of the type of vacuum equipment thatcan perform this function.

Downstream of the vacuum chamber 110 is a bonder 112. The bonder 112 canvary in design. The bonder 112 can be a mechanical bonder, ahydro-mechanical bonder, a thermal bonder, a chemical bonder, etc. Thebonder 112 is optional but for most non-woven webs 12 formed from verythin, randomly oriented fibers, the bonding step will provide addedstrength and integrity. When the bonder 112 is utilized, it will enhancethe integrity of the non-woven web 12 by forming spot bonds, pointbonds, zone bonds, etc.

It should be understood that the non-woven web 12 can be subjected toother mechanical or chemical treatment, if desired. For example, thenon-woven web 12 could be hydroentangled, be perforated, be cut, beslit, be punched, be stamped, be embossed, be printed, be coated, etc.After the bonder 112, if no other treatments are desired, the non-wovenweb 12 can be wound up on a supply roll 114. A cutter 116 can be used tocut, divide, sever or slit the non-woven web 12 at an appropriate lengthand/or width.

Referring again to FIG. 1, a distance d₉ is shown which is measured fromthe terminal tip 96 of each of the nozzles 58 to the moving surface 104.This distance d₉ is referred to those in the art as a “Die to CollectorDistance” (DCD). This DCD can vary depending on the type of equipmentused, the type of fibers 98 being formed, the operating conditions ofthe apparatus 10 or 10′, the polymer material 22 (polymer) beingextruded, the properties in the finished non-woven web 12, etc.Generally, the DCD can range from between about 10 centimeters (cm) toabout 150 cm. Desirably, the DCD can range from between about 20centimeters (cm) to about 125 cm.

Process

The process for forming a non-woven web 12 will be explained withreference to FIGS. 1, 2 and 11. The process includes the steps offorming a molten material 22 (polymer) and directing the molten material(polymer) through a die block 26. The molten material 22 (polymer) canbe a homopolymer or two different polymers with each being directed to acertain group of nozzles 58. Desirably, the molten material 22 (polymer)is polypropylene. The molten material 22 (polymer) is heated to atemperature of at least about 170° C. upstream of the die block 26,usually in an extruder 20. The die block 26 has a cavity 30 and an inlet28 connected to the cavity 30. The inlet 28 conveys a molten material 22into the die block 26. The die block 26 also has one or more gaspassages 32, 32 formed therethrough for conveying pressurized gas (air)to the spinnerette body 52. Each of the gas passages 32, 32, two beingshown, has an inside diameter d. An insert 34 is positioned in each ofthe gas passages 32, 32. Each insert 34, 34 has an inside diameter d₁and an outside diameter d₂. A major portion of the outside diameter d₂of each insert 34, 34 is smaller than the inside diameter d of each ofthe gas passages 32, 32 to form a chamber 48 therebetween. A spinnerettebody 52 is secured to the die block 26. The spinnerette body 52 has agas chamber 54 and one or more gas passageways 56, 56, two being shown,which connect the gas chamber 54 to the gas passages 32, 32. Thespinnerette body 52 has a plurality of nozzles 58 and a plurality ofstationary pins 62 secured thereto which are grouped into an array of aplurality of rows 64 and a plurality of columns 66, having a periphery68.

A gas distribution plate 70 is secured to the spinnerette body 52. Thegas distribution plate 70 has a plurality of first, second and thirdopenings, 72, 74 and 76 respectively, formed therethrough. Each of thefirst openings 72 accommodates one of the nozzles 58, each of the secondopenings 74 accommodates one of the stationary pins 62, and each of thethird openings 76 is located adjacent to the first and second openings,72 and 74 respectively.

An exterior member 78 secured to the gas distribution plate 70, awayfrom the spinnerette body 52. The exterior member 78 has a plurality offirst and second enlarged openings, 80 and 82 respectively, formedtherethrough. Each of the first enlarged openings 80 surrounds one ofthe nozzles 58 and each of the second enlarged openings 82 surrounds oneof the stationary pins 62. The array of nozzles 58 and stationary pins62 has at least one row 64 and at least one column 66, which are locatedadjacent to the periphery 68, being made up of the second enlargedopenings 82.

The process also includes directing pressurized gas (air) through theplurality of first, second and third openings, 72, 74 and 76respectively, formed in the gas distribution plate 70. The moltenmaterial 22 (polymer) is extruded through each of the nozzles 58 to formmultiple filaments 86. At least a portion of each of the multiplefilaments 86 is then shrouded by the pressurized gas (air) emittedthrough the first enlarged openings 80, formed in the exterior member78, at a predetermined velocity. The pressurized gas (air) exiting thesecond enlarged openings 82, formed in the exterior member 78, is usedto isolate all of the filaments 86 from surrounding ambient air.

Upon being extruded out the terminal end 96 of each of the nozzles 58,the filaments 86 start to solidify and are attenuated by the exitingpressurized gas (air) into fibers 98. An optional, second stage ofattenuation can be accomplished using an aspirator 100, see FIG. 11.When the aspirator 100 is utilized, the pressurized gas (air) in theaspirator 100 has a velocity which is at least twice (two time greaterthan) the velocity of the pressurized gas exiting the first and secondenlarged openings, 80 and 82 respectively. Desirably, the pressurizedgas (air) in the aspirator 100 has a velocity which is at least fivetimes greater than the velocity of the pressurized gas exiting the firstand second enlarged openings, 80 and 82 respectively. More desirably,the pressurized gas (air) in the aspirator 100 has a velocity which isat least ten times greater than the velocity of the pressurized gasexiting the first and second enlarged openings, 80 and 82 respectively.The filaments 86 are attenuated by the pressurized gas (air) which isdirected essentially parallel to the direction of flow of the filaments86. This is important because in other processes, especially in aconventional spunbond process, the attenuating gas (air) is directed atthe filaments at a steep angle. By keeping the attenuating gas (air)essentially parallel to the flow direction of the filaments 86, one canattenuate multiple rows and columns of the filaments 86 into fibers 98having unique properties and characteristics. Two of these uniquecharacteristics include forming small or fine diameter fibers 98, andforming fibers 98 which are much stronger than conventional meltblownfibers.

The fibers 98 are usually extruded as continuous fibers. The fibers 98are collected on a moving surface 104 to form a non-woven web 12. Themoving surface 104 can be a forming wire 106, a conveyor belt, arotating drum, a drum collector, a dual drum collector, etc.

The process can also include the step of subjecting the non-woven web12, while it is positioned on the moving surface 104, to a vacuum so asto remove process gas and ambient air, as well as limiting the fibers 98from flying around and thereby enhances web uniformity. The vacuum canbe supplied by a vacuum chamber 110 located adjacent to the movingsurface 104. Desirably, the vacuum chamber 110 is situated below themoving surface 104.

The process can further include the step of bonding the non-woven web12. The bonder 112 can be located downstream of the vacuum chamber 110or downstream of the location where the fibers 98 contact the movingsurface 104. The bonder 112 functions to bond individual spots, zones,lines, areas, etc. of the non-woven web 12 so as to increase theintegrity of the non-woven web 12. A cutter 116 can be positioneddownstream of the bonder 112. The cutter 116 serves to cut, sever, slitor separate one section of the non-woven web 12 from an adjacentsection. The cutter 116 can be any kind or type of cutting mechanismknown to those skilled in the art.

Lastly, the process can include rolling up the finished non-woven web 12onto a supply roll 114 such that it can be shipped to a manufacturingsite or location where the non-woven web 12 can be utilized. Thenon-woven web 12 can be used in a variety of products and for numerousapplications. Fine diameter fibers having good strength properties areespecially desired for use in various kinds of absorbent products, suchas diapers, feminine napkins, panty liners, training pants, incontinentgarments, etc. Fine diameter fibers having good strength properties canalso be used in acoustic insulation, thermal insulation, wipes, etc. Thefibers 98 can further be used in a variety of products.

Non-Woven Web

The non-woven web 12, produced on the apparatus 10 described above,contains a plurality of fibers 98 formed from a molten material 22(polymer). Desirably, the molten material 22 (polymer) is a homopolymer.More desirably, the molten material 22 (polymer) is polypropylene.Optionally, the non-woven web 12 could be formed from two or moredifferent polymer resins. Furthermore, the non-woven web 12 couldcontain bicomponent fibers.

The non-woven web 12 has an average fiber diameter which ranges frombetween about 0.5 microns to about 50 microns. Desirably, the averagefiber diameter ranges from between about 1 micron to about 30 microns.More desirably, the average fiber diameter ranges from between about 1micron to about 20 microns. Even more desirably, the average fiberdiameter ranges from between about 1 micron to about 15 microns. Mostdesirably, the average fiber diameter ranges from between about 1 micronto about 10 microns. The standard deviation for the average fibberdiameter should be above 0.5 microns.

The non-woven web 12 has a basis weight of at least about 0.5 grams persquare meter (gsm). Desirably, the non-woven web 12 has a basis weightof at least about 1 gsm. More desirably, non-woven web 12 has a basisweight of at least about 20 gsm. Even more desirably, non-woven web 12has a basis weight of at least about 50 gsm. Most desirably, thenon-woven web 12 has a basis weight above 100 gsm.

The non-woven web 12 has a tensile strength, measured in a machinedirection (MD), which ranges from between about 10 grams force per gramsper square meter per centimeter (gf/gsm/cm) width of the non-woven webto about 100 gf/gsm/cm width of the non-woven web. Desirably, thenon-woven web 12 has a tensile strength, measured in a machine direction(MD), which ranges from between about 12 gf/gsm/cm width of thenon-woven web to about 80 gf/gsm/cm width of the non-woven web. Moredesirably, the non-woven web 12 has a tensile strength, measured in amachine direction (MD), which ranges from between about 13 gf/gsm/cmwidth of the non-woven web to about 70 gf/gsm/cm width of the non-wovenweb. Even more desirably, the non-woven web 12 has a tensile strength,measured in a machine direction (MD), which ranges from between about 14gf/gsm/cm width of the non-woven web to about 60 gf/gsm/cm width of thenon-woven web. Most desirably, the non-woven web 12 has a tensilestrength, measured in a machine direction (MD), which ranges frombetween about 15 gf/gsm/cm width of the non-woven web to about 50gf/gsm/cm width of the non-woven web.

The fibers 98 forming the non-woven web 12 are randomly arranged.

The fibers 98 forming the non-woven web 12 can be bonded to increase theintegrity of the non-woven web 12. The fibers 98 can be bonded usingvarious techniques. For example, the fibers 98 can be mechanicallybonded, hydro-mechanically bonded, thermally bonded, chemically bonded,etc. Spot bonding, zone bonding, as well as other bonding techniquesknown to those skilled in the art can be used.

The following experiments were performed and show the uniquecharacteristics of the non-woven web 12 manufactured using the abovedescribed apparatus 10 and process.

Experiments

1. Inventive Non-Woven Web

The following nonwoven samples were produced using a pilot line that hadtwo 25″ dies with multi-row spinnerettes 52, 52 secured thereto,manufactured by Biax-FiberFilm Corporation having an office at N992Quality Drive, Suite B, Greenville, Wis. 54942-8635. Each spinnerette52, 52 had a total of 4,150 nozzles, each having an inside diameter d₃of 0.305 mm. Each nozzle 58 was surrounded by a first enlarged opening80 formed in the exterior member 78 where pressurized gas (air) wasallowed to exit. The inside diameter d₆ of each of the first enlargedopenings 80 was 1.4 mm. By comparison, a typical commercial spinnerette,manufactured by Biax-FiberFilm Corporation, can have from between about6,000 to about 11,000 nozzles per meter. Conventional meltblown material22 (polymer) was obtained from different vendors and the processingcondition and system parameters are disclosed in Table 1.

TABLE 1 Polymer Nozzle Basis Melt Gas Gas Polymer inside Weight DieTemp. Temp pressure DCD Throughput diameter Sample Polymer (gsm)Technology ° C. ° C (bar) (cm) g/hole/min (mm) S-1 Achieve 20.5 Biax-Old188 175 0.88 33 0.11 0.228 6936G1 Design S-2 Achieve 19.3 Conventional235 240 0.51 20 0.214 0.308 6936G1 MB die S-3 Achieve 20.1 Biax-New 200155 1.22 45 0.09 0.308 6936G1 Design S-4 Achieve 29.9 Conventional 235240 0.51 20 0.3 0.308 6936G1 MB die S-5 PP3155 30.8 Biax-New 300 5251.35 45 0.12 0.508 Design S-6 PP3155 30.1 Spunbond Die

2. Process Conditions

Several nonwovens webs were made using the above described pilot line.

Three different kinds of polymer resins were used. The first polymerresin was ExxonMobil polypropylene (PP) resin marketed under the tradename Achieve 6936G1. ExxonMobil Chemical has an office at 13501 KatyFreeway, Houston, Tex. 77079-1398. Achieve 6936G1 has a melt flow rateof 1,550 grams/10 minute (g/10 min.), according to American StandardTesting Method (ASTM) D 1238, at 210° C. and 2.16 kilograms (kg). Thesecond polymer resin was ExxonMobil polypropylene—PP3155. PP1355 has amelt flow rate of 35 g/10 min., according to ASTM D 1238, at 210° C. and2.16 kg. The third polymer resin was Metocene MF650W marketed byLyondellBasell. LyondellBasell has an office at LyondellBasell Tower,Suite 700, 1221 McKinney Street, Houston, Tex. 77010. Metocene MF650Whas a melt flow rate of 500 g/10 min. according to ASTM D 1238, at 210°C. and 2.16 kg. The process conditions of the different samples aredisclosed in Table 1.

3. Characterization Methods

3.1 Basis Weight

Basis weight is defined as the mass per unit area and can be measured ingrams per meter squared (g/m²) or ounces per square yard (osy). A basisweight test was performed according the INDA standard IST 130.1 which isequivalent to the ASTM standard ASTM D3776. INDA is an abbreviation for:“Association of the Non-Woven Fabrics Industry”. Ten (10) differentsamples were die-cut from different locations in the non-woven web andeach sample had an individual area equal to 100 square centimeters(cm²). The weight of each sample was measured using a sensitive balancewithin ±0.1% of weight on the balance. The basis weight, in grams/meter²(g/m²) was measured by multiplying the average weight by a hundred(100).

3.2 Fiber Diameter Measurements

To examine the fiber morphology and the fiber diameter distribution ofthe manufactured nonwoven webs, samples were sputter coated with a 10nanometer (nm) thin layer of gold and analyzed with a scanning electronmicroscope, model SEM, Phenom G2, manufactured by Phenom World BV havingan office at Dillenburgstraat 9E, 9652 AM Eindhoven, The Netherlands.Images were taken at 500× and 1,500× magnification under 5 kilovolts(kV) of an accelerating voltage for the electron beams. Fiber diameterswere measured using Image J software. “Image J” is a public domain,Java-based image processing program developed at the National Instituteof Health and can be downloaded from http://imagej.nih.gov/ii/. For eachsample, at least 100 individual fiber diameters were measured.

3.3 Fabric Tensile Strength

The breaking force is defined as the maximum force applied to a nonwovenweb carried to failure or rupture. For ductile material like nonwovenwebs, they experience a maximum force before rupturing. The tensilestrength was measured according to the ASTM standard D 5035-90 which isthe same as INDA Standard IST 110.4 (95). To measure the strength of thenon-woven web, six (6) specimen strips from each non-woven web werecutout at different locations across the non-woven web and each one hada dimension of 25.4 millimeters (mm)×152.4 mm (1″ by 6″). Each strip wasclamped between the jaws of the tensile testing machine which was aThwing Albert Tensile Tester. The clamps pulled the strip at a constantrate of extension of 10 inch/minute. The average breaking force and theaverage extension percentage at the breaking force was recorded for eachnon-woven web in the form of gram force per basis weight per width ofnon-woven web (gf/gsm/cm).

3.4 Air Permeability Measurement

Air permeability of non-woven fabrics is the measured airflow through anarea of the fabric at a specific pressure drop. Using the Akustron AirPermeability Tester, the air permeability was measured for the fibermats under a pressure drop equal to 125 Pa. Ten measurements for eachmat were recorded and the average values are reported herein. Thismethod of measuring air permeability is equivalent to the Frazier airpermeability testing method or the ASTM D737 test method.

Example 1

In this example, we were looking at the effect of spinning technology onweb properties. Three (3) different non-woven webs were made using thesame polymer resin. All three (3) had the same basis weight but each wasspun using a different spinnerette design and different processingconditions. As shown in Table 2, sample S-1 was produced using a Biaxmulti-row spinnerette design that did not have air insulation inserts 34or an air shrouding curtain (second enlarged openings 82) surroundingthe periphery 84 of the first enlarged openings 80. Sample S-2 wasproduced using a conventional meltblown process which had only one lineof nozzles along with inclined air jets. Sample S-3 was produced usingthe inventive process.

The sample S-3 achieved almost double the machine direction (MD) tensilestrength as compared to sample S-1 or sample S-2. Also, one will noticethat the fiber diameter of sample S-3 was slightly larger than the fiberdiameter of the conventional meltblown sample S-2. The primary reasonfor this difference in diameter is that when using the inventiveprocess, the colder air temperature in the annular channels is directedessentially parallel to the direction of flow of the filaments 86 in amulti-row fashion. In addition, by attenuating the fibers 98 usingcolder gas (air) one can increase fiber crystallinity and align themolecular chains inside the solidified fibers 98. This featurefacilitates attenuation of the filaments into strong, fine fibers 98. Ina conventional meltblown process, the attenuating air is introduced at asteep or inclined angle, using hot air jets.

Referring now to FIG. 12, another interesting feature of the non-wovenweb 12 manufactured according to this invention is the wide “FiberDiameter Distribution”. When one compares this “Fiber DiameterDistribution” to the “Fiber Diameter Distribution” of a non-woven webproduced using a conventional meltblown process, it is very clear thatthe standard deviation values and the “Fiber Diameter Distribution” arevery different. The main reason for this wide “Fiber DiameterDistribution” in our apparatus 10 is the use of a multi-row spinnerettedesign. The filaments 86 exiting the nozzles 58, located with theperiphery 84, see FIG. 10, are not exposed to the surrounding ambientair and a quick quench time, and therefore these filaments 86 tend tostay hotter longer and thereby produce finer fibers 98 than thefilaments 86 that are extruded from nozzles 58 located in the outsiderows of a spinnerette body 52. By replacing the nozzles 58 with thestationary pins 62 in the outside rows 64, located adjacent to theperiphery 68, see FIG. 7, an air curtain or shroud is formed around theplurality of extruded filaments 86. This air curtain or shroud delaysthe interaction of the surrounding ambient air with the extrudedfilaments 86. This delay prevents the early solidification of the moltenpolymer streams at the terminal tip 96 of each nozzle 58 and reducesshots and roping defects that are encountered when the old Biaxmulti-row spinnerette was used. This earlier multi-row spinnerette istaught in U.S. Pat. No. 5,476,616. By “shot defect” it is meant small,spherical particles of polymer formed during the web forming process.Table 2 also shows that air permeability of the spunblown sample S-3 wasat least 50% higher than the conventional meltblown sample S-1 that wasproduced at the same condition. The main reason for such an increase isthe larger fiber diameter and the wider fiber diameter distribution thatis reflected in the fiber size standard deviation.

TABLE 2 Samples performance of Example 1 Machine Machine Cross CrossStandard Direction Direction Direction Direction Air Fiber DeviationElongation Strength Elongation Strength Permeability Sample Size, μm μmPercent (%) gf/gsm/cm Percent (%) gf/gsm/cm m³/m² · min S-1 2.77 1.7713.44 12.13 87.45 9.33 18.6 S-2 1.66 0.82 17.77 10.28 24.11 9.96 11.1S-3 2.23 1.57 23.84 20.24 88.94 7.54 17.4

It should be understood that the fibers 98 in the non-woven web 12 canto have a Standard Deviation of from between about 0.9 microns to about5 microns. Desirably, the fibers 98 in the non-woven web 12 have aStandard Deviation of from between about 0.92 microns to about 3microns. More desirably, the fibers 98 in the non-woven web 12 have aStandard Deviation of from between about 0.95 microns to about 1.5microns.

Example 2

In this second example, we were comparing a sample produced by theinventive process S-5 to a sample produced by a conventional meltblownprocess S-4, and to sample produced by a conventional spunbond processS-6. Three (3) samples were made and each had the same basis weight. Asshown in Table 3, the properties of sample S-5 were about half-waybetween the properties of the meltblown web S-4 and the spunbond webS-6. Table 3 also shows that the air permeability of the sample S-5(using our inventive process) falls almost half-way between theconventional meltblown sample S-4 and the conventional spunbond sampleS-6. This proves that our new technology is capable of producingnon-woven webs that have fine fiber diameters, comparable to meltblownfibers, yet strong as compared to spunbond fibers.

Referring to FIG. 13, the machine direction (MD) tensile strength of thenon-woven web 12 of this invention (sample S-5) was more than double theMD tensile strength of the meltblown web sample S-4 and almost half theMD tensile strength of the spunbond web sample S-6. Another noticeablefeature was that the extensibility of the non-woven web 12 of thisinvention (sample S-5) was almost triple the extensibility of themeltblown web sample S-4 and similar to the extensibility of thespunbond web sample S-6.

From the above two examples, it is clear that a non-woven web 12 madeusing our inventive apparatus and process is unique and has propertiesthat are about half-way between the properties exhibited by a non-wovenweb made using a conventional meltblown process or a non-woven web madeusing a conventional spunbond process.

Furthermore, the apparatus 10 of this invention is flexible andversatile enough to use a wide variety of polymeric resins to produce awide range of non-woven webs. The apparatus 10 can be operated usingmeltblown grade resins and well as spunbond grade resins.

TABLE 3 Samples performance of Example 2 Machine Machine Cross CrossStandard Direction direction Direction direction Air Fiber DeviationElongation Strength Elongation Strength Permeability Sample Size, μm μmPercent (%) gf/gsm/cm Percent (%) gf/gsm/cm m³/m² · min S-4 2.33 1.3515.19 10.2 33.49 16.25 7.2 S-5 4.39 2.98 41.02 21.24 62.86 15.96 53.7S-6 19.48 1.49 41.35 51.56 46.16 49.39 135.8

While the invention has been described in conjunction with severalspecific embodiments, it is to be understood that many alternatives,modifications and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, this inventionis intended to embrace all such alternatives, modifications andvariations which fall within the spirit and scope of the appendedclaims.

We claim:
 1. A nonwoven web comprising a plurality of fibers formed froma molten polymer having an average fiber diameter ranging from betweenabout 0.5 microns to about 50 microns, a basis weight of at least about0.5 gsm, and a tensile strength, measured in a machine direction,ranging from between about 12 gf/gsm/cm width of said non-woven web toabout 100 gf/gsm/cm width of said non-woven web.
 2. The non-woven web ofclaim 1 wherein said average fiber diameter ranges from between about 1micron to about 30 microns.
 3. The non-woven web of claim 1 wherein saidaverage fiber diameter ranges from between about 1 micron to about 20microns.
 4. The non-woven web of claim 1 wherein said average fiberdiameter ranges from between about 1 micron to about 10 microns.
 5. Thenon-woven web of claim 1 wherein said molten polymer is a homopolymer.6. The non-woven web of claim 1 wherein said non-woven web is formedfrom two different polymer resins.
 7. The non-woven web of claim 1wherein said plurality of fibers in said non-woven web have a standarddeviation which ranges from between about 0.9 microns to about 5microns.
 8. The non-woven web of claim 1 wherein said fibers arerandomly arranged.
 9. The non-woven web of claim 8 wherein said fibersare mechanically bonded.
 10. A nonwoven web comprising a plurality offibers formed from a molten homopolymer having an average fiber diameterranging from between about 0.5 microns to about 50 microns, with a basisweight of at least about 0.5 gsm, and a tensile strength, measured in amachine direction, ranging from between about 12 gf/gsm/cm width of saidnon-woven web to about 80 gf/gsm/cm width of said non-woven web.
 11. Thenon-woven web of claim 10 wherein said fibers are hydromechanicallybonded.
 12. The non-woven web of claim 10 wherein said fibers arethermally bonded.
 13. The non-woven web of claim 10 wherein said fibersare chemically bonded.
 14. The non-woven web of claim 10 wherein saidaverage fiber diameter ranges from between about 1 micron to about 10microns, and said tensile strength ranges from between about 13gf/gsm/cm width of said non-woven web to about 70 gf/gsm/cm width ofsaid non-woven web.
 15. The non-woven web of claim 10 wherein saidhomopolymer is polypropylene.
 16. A nonwoven web comprising a pluralityof fibers formed from a molten homopolymer having an average fiberdiameter ranging from between about 1 micron to about 50 microns, abasis weight of at least about 1 gsm, and a tensile strength, measuredin a machine direction, ranging from between about gf/gsm/cm width ofsaid non-woven web to about 50 gf/gsm/cm width of said non-woven web.17. The non-woven web of claim 16 wherein said average fiber diameterranges from between about 1 micron to about 30 microns.
 18. Thenon-woven web of claim 16 wherein said average fiber diameter rangesfrom between about 1 micron to about 15 microns.
 19. The non-woven webof claim 16 wherein said average fiber diameter ranges from betweenabout 1 micron to about 10 microns.
 20. The non-woven web of claim 16wherein said fibers are randomly arranged and mechanically bonded.